Production of phosphorus



- Jan. 15, 1935. A. J. MASON 1,988,387

PRODUCTI ON OF PHOSPHORUS Filed Aug. 27, 1930 6 Sheets-Sheet l Jan. 15, 1935.

A. J. MASON 1,988,387

PRODUCTI ON OF PHOSPHORUS Filed Aug. 27, 1930 s Shets-Sheet 2 m .YA

'urflpezzz or' a g m Jan. 15, 1935. A. J. MASON 1,988,387

PRODUCT ION OF PHOSPHORUS Filed Aug. 27, 1930 6 Sheets-Sheet 3 Jan. 15, 1935.

A. J. MASON PRODUCTION OF PHOSPHORUS Filed Aug; 27, 1930 6 Sheets-Sheet 4 Jan, 15, 1935.

' A. .1. MASON PRODUCTION OF PHOSPHORUS Filed Aug. 2'7, 1930 6 Sheets-Sheet -5 'kyfggenzor' 5% 7" 63607? V \I I Jan. 15, 1 935. A. J. MASON 1,988,387

PRODUCTION OF PHOSPHORUS Filed Aug. 27, 1930 6 Sheets-Sheet 6 Patented Jan. 15, 1935 UNITED STATES PATENT o lraonuc'rron 0F rnosrnorws ArthunJ. Mason, Homewood, 11].; Continental 'Illinois'National Bank and Trust Company of Chicago, executor of Mason,:deceased estate of said Arthur J.

Application August .27, 1930, Serial 'No. 478,194 3 Claims. (01. 23-223) The'present invention relatesto improvements in the recovery of, the phosphate :values of mineral phosphates in the form "of phosphorus or compounds thereof, such as zphosphoric acid or phosphorus 'zpcntoxide, .and more particularly to such :processes'wherein the phosphorus content of thevm'ineral is reduced and'volatilized-by the "use ofsa suitable :carbonaceous material.

Volatilization :processes for .the recovery of the phosphorus values 'from .zphosphates have hitherto been attended with many serious disadvantages. such processes of which the blast furnace 'type of operation-is typical, high temperatures of operation are required, and the "attainment of "such temperatures :can be secured "effectively only by thecombustion of the fuel employed with a reasonable efficiency so as to produce substantial amounts of carbon dioxide. This carbon dioxide, in the quantities present, in turn serves as an oxidizingagent for the carbonaceous material present the reaction "zone in which the :reduction of the phosphate of the :mineral is to be effected and consequently necessitates the introduction: of 'excessive quantities' of the reducing agent and lowers the efficiency :o'f the reducingv operation.

of which would be highly desirable from the "standpoint :of efficiency and: economy.

The high .temperatures employed in such volatilization processes as "hitherto proposed l'for JpracticaI usepandrequiredifor the fusion of the slag and. ferrous constituents of the reaction mixture, have the "further disadvantage of .inducingsa considerable loss of phosphorus by reaction withriron and other metallic constituents of the mixture with the formation :of'the corresponding phosphides, such: asiferrophosphorus. Thusferrophosphorus containing as "high'as 25 tol30% :of the phosphorus may'fbe' formed-as a fiby-product of such "processes. 1

The present inventionhas as its object "a reduction process for the recovery andremoval of the phosphorus values of a phosphorus-containing mineral, employing --car-bonaceous material as reducing agent and ,as-fuel, which iswnot .attended with the disadvantagespf :such pr.o-

cesses as hitherto carriedout. As an important feature-of the invention, I separate the time periods of heating the furnace employed andm f heating the phosphatic charge therein. l prefer to employ as the furnace ,a-refractory-walled chamber, and while it may be rexteriorily heated,

.I prefer to heatit interiorily by the application of hot gases or "by interior combustion ofifuel gases or preferably of phosphorus-containing gases resulting from thephosphate reductionoperation. A sufiicient heat is storedin the-walls of 'the chamber, heating thereof-is :then stopped,

and the phosphatic charge introduced and areduction and volatilization of the phosphorus *ef- .rfected. In this, reduction :and volatiliza-tion,

heat is absorbed from the walls-10f the reaction chamber and after discharge of .-thespent reace tion mixture, "thereaction chamber is again heated andthe operation repeated. {prefer to utilize a system containingtwo ior'morezreac :tion chambers, the gases-evolved in-ionexduring the reduction and volatilization :process "being burned in :another to convert their phosphorus content into phosphorus pentoxide and at the same, time to supply the necessary rheatzforgzits interior Walls to 'bringit to the necessary item.- perature .for conducting in it a'rreduction and yvolatilization operation upon another-charge.

-In operating in accordance with zmyiinvention,

the reduction and volatilization is ;effected in .a substantially quiescent atmosphere, preferably of a reducing character and consisting largely of carbon .-monoxide,, andflwithout passage through the charge of the-large yvolumesxof combusti'on gases or dilution of the :phosphorus therewith, as in fuel-fired zvolatilizationtopera- *itionsihitherto commercially employed. 1 :Iiprefer to conduct the operation without,zfusiontzof the =reaction mixture, and thereby avoid the necessity' of incorporating into the -charge -';large;pro

portions of fluxesv or slag-formingconstituents and prevent the combination (of phosphorus with the metallic constituents of the #charge,

such-as iron, to a veryigreat extent. :Byxpre- :paring the charge as herein-set-forth, :I;S6ure an intimate contact of the-phosphate rock 1-.in

the finely-divided, incandescent ijcarbonizduning reactioni and thereby greatly facilitate ;reduc=- tion. In order that the invention cmayi herfully V6111; loss of heat.

understood, I have described it hereinafter in connection with certain specific embodiments of apparatus suitable for carrying it into effect, but it will be understood that these details of apparatus and of specific procedure therein are not intended to be regarded as limitations upon the scope of the invention, since obviously numerous other forms of apparatus and other details of procedure may be employed.

Figure 1 is a side elevation of apparatus suitable for carrying the invention into effect;

Fig. 2 is a plan view of a portion of the appa ratus, showing a pair of reaction furnaces;

Fig. 3 is an enlarged elevation, partly insection, of a portion of the preheating or carbonizing furnace; and

Fig. 4 is an enlarged sectional. view of an- 7 other portion, the discharge end, of the preheating or carbonizing furnace; Fig. 5 is a vertical sectional view through the reaction {furnaces on the line 5 of Fig. 1;

6 is a vertical sectional view through a portion'of the receiving end of a reaction furnace, on the line 6 of Fig.2; and

Fig. '7 is a vertical sectional view through another portion,*the discharge end, of a reaction furnace on the line 7 of Fig. 2; Y Fig. 8 is a transversesectional view on the line 8 of Fig. 6; and Fig. 9' is a transverse sectional view on the line '9 of Fig.7; and

-Figs. 10 and 11 are respectively vertical and horizontal sectional views through an air preheater employed in the present invention.

- i In the drawings, the numeral 15 designates a fired furnace setting for a preheating or carbonizing furnace, suitably such as that described in my prior application Serial No.

441,547, filed April 4, 1930. This furnace is provided with an elongated chamber 16, through which pass thecombustion gases from the fur-y nace' portion 17. A rotatable cylindrical furnace 18 having a downward inclination extends longitudinally through the furnace chamber 16, and.

is provided at its receiving end with a closure 19 upon which is mounted the drive gear 20.

A stationary trunnion 21 passes through the closure member 19, opening into the interior of the rotatable furnace 18, the charge, composed as hereinafter described, being fed through the trunnion 21 by any-suitable means, such as the screw 22; The charge-is initially delivered to a receiving hopper 23 and is passed successively through Y chambers 24 and 25, provided with valve closures 26, which may be alternately operated in the customary manner to feed the charge without permitting escape of gases. From the chamber 25, the charge is picked up by the screw 22'to be fed into the furnace 18.

' JAt its discharge end, the furnace 18 opens into a receiving chamber 27, suitably with heavy refractory walls to serve as insulation and pre- In the upper portion of the rotatingfurnace 18, a cutter bar support 28 is provided, being pivotally:mounted at one end -on 'a bracket 29 on the trunnion 21. and at the other end on a bracket 30 carried by the wall of the receiving chamber 27, the cutter bar '28 being provided with a tool steel cutter edge31 extending the length of the rotating furnacev 18,

and being so mounted-thatthe cutter edge 31 is held-in juxtaposition to the wall of the "cylindrical chamber 18 onthe ascending side thereof, as morefully set forth "in. my prior application Serial-N0f' '441-,547, hereinbefore referred 9 .of the reaction furnace.

I feed to the preheating and carbonizing furnace 18 a charge consisting of the phosphate -Thus, I may employ a mixture of about equal proportions of mine-run Tennessee phosphate rock and bituminous coal. Such a charge is fed to the hopper 23, passes throughthe chambers '24 and 25, and forced into the preheating and carbonizing furnace 18 .bymeans of the screw 22. The furnace 18 is rotated and is heated to a suitable temperature, say 1000 to 1200 F., the carbonaceous material therein is partially or wholly coked, and volatile and liquefied constituents of the coal permeate the mass, resulting in an intimate associationrof carbonaceousmaterial and-finely divided phosphate rock throughout the entire body of material. By the com: bined action of the rotation of' the furnace and of the cutter bar 31, the mixture is agglomerated into small granules or lumps The gases from the preheating operation together with the agglomerated material pass -.:into' the receiving chamber 27, the reaction" mixture beingthen at a temperature of say 900 to 1100 F. and prefably about 1000" F; The gases, from the preheating operation are drawn off through .the pipe 32 and are utilized in the system as hereinafter set forth.

The hot lumps or granules of reaction mixture pass out of the chamber 27 through an opening controlled by bell valve 33 into a refractory walled chamber 34, and from the latter through .an opening controlled by bell valve 35 into achamber 36 provided with two discharge spouts 37 and 38, controlled by valves 39 and 40 respectively. By the discharge spouts 37 and 38'the reaction mixture may be directed to either. of

two reaction furnaces 41 and-i42,=-of similar construction. rFor simplicity,.'the corresponding,

parts of these reaction furnaces will be designated by identical numerals.

Each of the reaction furnaces 41. and 42 is formed of a cylindrical bodyportion 43 of refractory material, provided at one end with a receiving head .44 and at the otherrend with a discharge head 45, the entire furnace being enclosed by a metallic casing'46. On this casing there are provided the supporting rings 4'7 carrying the ring-gears 48, the furnacebeing sup-- attainable, so that it will rapidly store up-a considerable quantity ofheat and readilyfyieldit up. Refractories. such as carborundum and magnesite have beenfound suitable.

The receiving head 44 of each furnace is provided internally withan, annular. pocket 49 of irregular section, as best shown in'Figp8, this pocket being formed with'an innercylindrical wall concentric with the axis of the furnace and an outer'. wall 51 eccentric thereto. Inconsequence, the pocket 49 has a constricted portion 52, and from this constricted portion a port 53 is provided opening into the cylindrical body "43 At a larger portion thereof, the pocket49 is provided with a port 54 l 1 vrhsa aw extending laterally ithroughfithe body of the receiving headsandzclosediby a; gate55 thecasing 46; therporti' 54i.and.-gatei55:,beingin such acpositi'on that, whenirequired, .they 'maybebrought in 37==or "=38, as the 'case may be, toxreceive the -charge:for the furnace.

The discharge head 45 is likewiseprovided in- "zternallywith an annular pocket 56, formed with concentric walls. :At one point, this pocket :is :provided withi-a port-57 extending to the: interior .-o'f' the'icylindrical body '43 of the furnace at-its ':lower'2end,:to:receive'material from the furnace. At anotherlpoint, the pocket 56 is provided with 5 .tinrthepasing of the furnace, andfthrough'which :r'naterialv may be dischargedifrom the pocket.

:Inrthe. operation of either furnace, for exvample the:furnace 41, it is 'preliminarilyheated to .bring the interior walls: in'the. effective :reacxtionrjzone :near one end to a: temperature substantiallyabove 1200 C. andpreferably'to .1400 i.tojl500iC.,'this preheating-being preferably effected by the combustion in the furnace of .phos- 1phoruscontaining 'gases derived from another operationxor of combustiblegasesfrom the pre- :heating and'carbonizing operation already de- -=,s'cribed,;orq-both. The preferred manner of this ,preheatingawilL-be: hereinafter more full set forth. .After therinterior:oftthe furnacehas been suitablymre'heated, a-charge of thereaction mixture .-of-iphosphatemineral and thecarbonaceous ma- --terial,is.introducedrinto-the.pocket 49 inthe receiving .head44 of thexifurnace. The preferred reaction -mixture is 'the .agglomerated material derived from the preheating and carbonizing operation above set forth and is delivered. from .rtionnin lzthis manner, :a minimum r of extraneous juxtaposition .toxthe-opening'of one of the spouts gasa'isipresent and afhigh concentration .of:.phos-, :phorus vapor:in the evolved gases is secured. Asitreaches :thedischarge end of thet-furnace, :the: spent 3 reaction mixture is discharged progressively :from the body of the furnace through the port-.57 intothe pocket 56, inwhichitxaccumulates until theentire charge'fedsinto "the receivingflhead 44 :has passed throughthe furnace'and:beentreated. This charge is solad- .justedzthat thestoredheatin the wallsxof the a laterallyextendingport.57, closedby a gate :58 1

furnace will effect ithe 'desired reaction. When therspent reaction-*mixture has-been completely aaccumulatedin -the:pocket 56, the furnaceis'rotated until "the gate :-58::is lowermost, andrthe ig-ate isrthen .opened-itodischarge the spentreac- ,tion- .mixture. T Heating may be resumed as soon as the-spent charge 1 reaches "the pocket 56.

In carrying out the invention, it is preferred: to

employ "a plurality of reaction .furnaces, for ex- I ample, two, as shown in' the drawings, a and while carrying,zoutthe'zreaction in one of the furnaces,

I 1 directing the evolved vvapors therefrom. into anotherifurnace v and. burning them therein to con- ;na-cewinteriorly to' the required temperature if or 1 verttheir phosphorus content intophosphorus pentoxide, and at thessame time .heat such furcarryingxout-thereaction. Whenreaction in the firstfurnaceceases and the react-ionima'terial is discharged, or. during thezperiodqof its discharge, the reaction mixture having been. charged into the second :furnace, thereaction is conducted thereiniand the evolved vapors directedinto and --burned ingthefirst furnace, in. a similar manner.

+the receiving: chamberi2'lr of said furnace through Furthermore,v as hereinbefore indicated, the 'gases ,evolved from the preheating furnace may be employedzduring a 'portion'of the operationofnipreheating the :reaction furnace.

In the drawings, connectionssuitable for such purposes are illustrated. :Reheatingof either furnace may beabegun assoon as theicharge thereinhas completedits reactionand during or afterdischarge of the spent reactionzmaterial. .In the lay-out shown in .the drawinga and best seen in1Fig. 2,, it ;will beassumed that reaction is about to take place'in the furnace 41,

the furnace-42: having just: been-emptied of spent ,3

reaction'mixture. and being ready forpreheating.

fusion, isuch temperature being from 11100 to 1:3.00 C.,.andrpreferably :about 1200 :C. The :phosphorus' is released from' the reactionimixture ;in an atmosphere almost completely of carbon monoxide, an excess of carbonaceous material -being,supplied to maintain suchan atmosphere, since Ihave found that, at'such-re'latively low, nonfusiontemperatures above referred-to,=in the presence-of an atmosphere of carbon monoxide, substantially complete reduction and volatilization of the phosphorus-content of the mineral is-effected. "Under these "conditions, there isno appreciable fusion or slagging of the reaction mixture, and the spent reaction mixture is of about the same order of fineness or even finer than the reaction mixture chargeds ,Du'ringthe F0r.a:;short period after thezrea'ction mixture has been fedito thefurnace '41, and before the initial portions of it passing through the furnace reach reaction temperatures, there is no evolution of combustible vapors therefrom. Duringithis. period, combustible gas from :the preheating and. carbonizing --furna'ce' 15, which is continuously operated, is discharged through thepipe 32 andenters aoonduit -60,:fro'm"which a valved :branch ;line 61% leads toza trunnion 62, which passes :centrally through the discharge head 45 of the furnacei42; Air=ifor the combustion of'this' gas is delivered'bya pump 64, by

which .it is :forced through .an air preheating .q;

yfurnace. 65, ,being discharged :therefrom :through period of reaction,therotatingfurnace is sealed at .its lowennd, as hereinafter set forth, and the phosphorus vapors, together with carbon monoxide andany other gases evolved, pass out 4 through an opening 59 provided centrally of the receivingheacLfor recovery of the-phosphorus or d Q Ir F e i-tO. rh ss o usy e to ide,

, containingcombustible gas fronr-the furnace-il the;hot;air-line 66, fromwhich avalved branch 167.1eads tosthetrunnion5.62:

Assoon as the evolution of the: phosphorus- 7 begins, :thehydrocarbon fuelgas fromthe car- ;bonizingrfurnace is diverted and provisionis made; ;:for theintroduction offthe phosphorus- *containingelgas. into the dischargeaend'of the furmace: hen such, diversiom is. to; be :eiliec'ted, 27 5 the valved line 62 fromthe gas conduit Combustion of the hydrocarbon fuel gas from the carbonizing furnace 17 is then continued in :furnace 42,

the air preheating furnace 65, the air passing through a coil 73 provided therein, until the hydrocarbon gasis requiredin the initial stages of preheating of the furnace 41, when it is diverted for-that purpose, as hereinafter set forth.

The hydrocarbon gas no'longer passing to the the phosphorus-containing gas which isevolved from the furnace 41 and passes out of the latter througha trunnion 74 at its receiving end, is caused to flow through a valved connection 175 to a conduit 76. A. second valve connection 77 to the trunnion 77 is closed at this time, its function being hereinafter set :forth. c

From the conduit 76, the phosphorus-contain- -ing gas passes through a valved connection 78 to the trunnion 63,'being mixed withthe preheated. air which. is still being suppliedthrough the valved connection 67. The phosphorus-containing gas is burned in the furnace 42,bringing -it:tothe desired operating temperature, preferablyaround .1400 to 1500 .0. near its-discharge end, where combustion takes place, the temperature being lower at the receiving end which serves as a preheating zone utilizing the heat of the combustion. gases as they travel through the furnace. The temperature at the receiving end of the furnace will ordinarilybe 600 to 700 C. The burned vapors and gases from the furnace 42 during the entire preheating period pass out through the trunnion 74 which is provided with two valve connections. The valve connection 75 which corresponds to the connection 75 on the furnace 41, is closed and the valve connection 77 is open. The connection 77 is provided with two branches. During the period of combustion of the hydrocarbon gas from the preheating and carbonizing furnace 15 in the reaction furnace 42, the connection 78 is opened,

to permit discharge of the combustion gases to the stack. When the hydrocarbon gases are diverted: fromthe reaction furnace 42 and'com- 'bustion .of phosphorus-containing gas begins therein, the. connection 78 is closed and theconnection 79 opened, the latter leading to suitable scrubbing and precipitating devices for removing phosphorus pentoxide or phosphoric acid from the gases.

When the reaction in the furnace 41 is completed, at which timethe furnace 42 has been preheated to the desired temperaturejrotation of the furnace 41 is-stopped for the discharge of the spent reaction mixture as hereinbefore described, the connection75. to the trunnion 74 for dischargeof.phosphorus-containing vapors having been closed.- At the same time, the valve connections 67 and 78 to the trunnion 63 of furnace 42 are closed, and. the latter is charged with a batch of reaction mixture, which is 7 caused to travel through the furnace, gradually attaining reaction temperature. Operation of furnace 42 is then started for the conduct of the reaction. The furnace 41 is preheated in' a manner. similar to-that described-in connection withthe preheating of furnace 42. The air con-. nection 67 and the gas connection '62 from the gas conduit 61,.both leading to the trunnion 63 vapors are evolved from the furnace 42. At this time, the gas connection 62 is. closed, the gas .being diverted to' the'burners and air preheater 65 as above described, and the phosphorus vapor' connection from the trunnion 74- of furnace 42 is opened. The connection 75 from the trunnion 74 of the furnace 41 is closed at this time, and the phosphorus vapors from the furnace 42 pass out through the connection 75, the phosphorus conduit 76, and are directed through the connection 78 to'the. trunnion 63 of furnace 41. During the preheating-period in the furnace 41, the connection 77, the trunnion 74 is opened, leading through connection.'79 to the stack during the period in which gas from the carbonizing and preheating furnace 15 is burned in the furnace 41 and through'the connection 80 to the phosphoric acid scrubbers and precipitators during the period in whichphosphorus-containing vapors are being burned in the furnace 41.

In this manner, reaction is caused to take place alternately in the furnaces 41 and 42, and

a during reaction in either, the other is preheated to the necessary temperature," preferably by combustion therein of the gases evolved from the furnace in whichreaction is taking place. Al-

though specifically described in connection with a lay-out containing two furnaces, it isreadily apparent that additional furnaces may be employed, with proper control of the reaction and preheating periods therein with respect to one 7 phosphorus-containing. vapor therefrom, conducting said phosphorus-containing vapor into a second reactionchamber and burning it therein, internally heatingfthe walls of the second reaction chamber, and ontermination ofthe' reaction and evolution .of phosphorus-containing vapor inthe first reactionv chamber, and the heating of the second reaction chamber, charging a reaction mixture of phosphate and reducing agent into the second reaction chamber wherein it is heated solely by contained heat of the walls thereof, and conducting the phosphorus-containing vapors evolved from the second reaction chamber to the first reaction chamber .to be burned therein to supply heat therein for" further reaction.

2. In the art of producing phosphorusr heating a mixture of phosphate mineral and coking coal to a coking temperature, thereby forming a reaction mixture of phosphate and carbonaceous material, preheating the interior walls of a reaction chamber to reaction temperature, then charging into said reaction chamber the reaction mixture, whereby it is heated therein solely by contained heat of the walls of e the reaction chamber and the phosphate content of the reaction mixture is reduced and the resulting phos- .phorus' evolved, conducting the resulting phosphorus to a second reaction chamber, burning it therein to heat its walls to reaction temperature,and thereupon supplying reaction mixture to the second reaction chamber'for similar treat- ;ment therein.

' 3. In the art ofproducing phosphorusf the .method whichcomprises heating a mixture of phosphate rock and coking coal to a coking temperature, thereby producing a combustible hydrocarbon gas and a reaction mixture of phosphate and carbonaceous material, preheating a reaction chamber to reaction temperature, and thereupon charging said reaction mixture into the reaction chamber, whereby the reaction mixture is heated therein'until it attains reaction temperature and to effect reaction with evolution of phosphorus-containing gases, conducting combustible hydrocarbon gases from the initial heating of the reaction mixture and coking coal into a second reaction chamber and burning them therein until the reaction mixture in the first reaction chamber begins evolving ber and burning them therein, thereby preheat-.

ing the second reaction chamber internally to reaction temperature, and thereupon discontinuing the heating of the second reaction chamber and introducing the reaction mixture of phosphate and carbonaceous material thereinto, for reduction and evolution of its phosphorus content.

ARTHUR J. MASON. 

